<template>
  <header class="header">
    <h1>todos</h1>
    <input id="toggle-all" class="toggle-all" type="checkbox" >
    <label for="toggle-all"></label>
    <input
      class="new-todo"
      placeholder="输入任务名称-回车确认"
      autofocus
      v-model.trim="str"
      @keyup.enter ="addTodo"
    />
  </header>
</template>

<script>
export default {

 data() {
   return {
     str: '',
   };
 },
 methods:{
 addTodo( ){
   if(this.str.length===0)return alert("输入内容不能为空")
   this.$emit("add",this.str)
    this.str=''
 }
 }
}
</script>